Split index interface and registry implementation

solidity/AccountsIndex.sol

@@ -4,9 +4,9 @@ pragma solidity >0.6.11;
 
 contract CustodialAccountIndex {
 
-	address[] public entry;
-	mapping(address => uint256) public entryIndex;
-	uint256 public count;
+	address[] entries;
+	mapping(address => uint256) entryIndex;
+	uint256 count;
 	mapping(address => bool) writers;
 	address public owner;
 	address newOwner;
@@ -16,7 +16,7 @@ contract CustodialAccountIndex {
 
 	constructor() public {
 		owner = msg.sender;
-		entry.push(address(0));
+		entries.push(address(0));
 		count = 1;
 	}
 
@@ -32,29 +32,38 @@ contract CustodialAccountIndex {
 		return true;
 	}
 
+	// Implements AccountsIndex
 	function add(address _account) external returns (bool) {
 		require(writers[msg.sender]);
 		require(entryIndex[_account] == 0);
-		entry.push(_account);
-		entryIndex[_account] = count;
-		count++;
-		emit AccountAdded(_account, count-1);
+		entryIndex[_account] = entries.length;
+		entries.push(_account);
+		emit AccountAdded(_account, entries.length-1);
 		return true;
 	}
 
+	// Implements AccountsIndex
 	function have(address _account) external view returns (bool) {
 		return entryIndex[_account] > 0;
 	}
 
-	function entryCount() public returns (uint256) {
-		return count;
+	// Implements AccountsIndex
+	function entry(uint256 _idx) public returns (address) {
+		return entries[_idx+1];
 	}
 
+	// Implements AccountsIndex
+	function entryCount() public returns (uint256) {
+		return count - 1;
+	}
+
+	// Implements EIP173
 	function transferOwnership(address _newOwner) public returns (bool) {
 		require(msg.sender == owner);
 		newOwner = _newOwner;
 	}
 
+	// Implements OwnedAccepter
 	function acceptOwnership() public returns (bool) {
 		address oldOwner;
 
@@ -65,6 +74,7 @@ contract CustodialAccountIndex {
 		emit OwnershipTransferred(oldOwner, owner);
 	}
 
+	// Implements EIP165
 	function supportsInterface(bytes4 _sum) public pure returns (bool) {
 		if (_sum == 0xcbdb05c7) { // AccountsIndex
 			return true;